Examples of a vehicular arm component include a suspension arm which connects a vehicle body and a wheel and a radius rod which connects a subframe and the wheel. Such a vehicular arm component is required to nave a sufficient tensile strength in order to oppose a large tensile force applied during running or braking of the vehicle.
It is desired to increase ride comfortableness by avoiding (releasing) oscillations by preventing direct transmission of the oscillations during external force input to a driver while the above condition is satisfied. In order to avoid oscillations, it is necessary to absorb oscillations with a vehicular arm component by increasing the amount of displacement of (by deflecting) the vehicular arm component during external input. It is important to properly reduce the rigidity of the vehicular arm component.
In order to reduce the rigidity, it is effective to reduce the material thickness of the vehicular arm component or that a shaft portion of the vehicular arm component has an open cross-section. For example, Patent Literature 1 below discloses a suspension arm in which an axially formed opening is provided in a part in the circumferential direction. With the suspension arm configured in the above manner, the shaft portion of the vehicular arm component has an open cross-sectional shape. Therefore, the torsional rigidity can be reduced. Thus, the amount of displacement of the suspension arm during external input can be increased, enabling avoidance of oscillations during external input, thereby increasing the ride comfortableness.